Production of 2-phenylpentane



United States Patent PRODUCTION OF Z-PHENYLPENTANE David A. McCaulay, Chicago, 11]., and Arthur P. Lien, Highland, InrL, assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana N 0 Drawing. Application November 17, 1953, Serial No. 392,756

Claims. (Cl. 260-671) This invention relates to the production of Z-phenylpentane. More particularly the invention relates to the conversion of his (3-pentyl-) benzene to Z- henylpentane.

In the petroleum industry it is frequently desirable to convert a higher boiling hydrocarbon into a lower boiling hydrocarbon, or convert a low boiling hydrocarbon and a high boiling hydrocarbon into a single hydrocarbon boiling intermediately between the reactants.

1,4 bis (3-pentyI-) benzene boils at about 268 C. This is considerably beyond the gasoline range. Phenylpentane boils within the gasoline range. Owing to the high octane number of alkyl aromatics, the addition of such an aromatic to the higher boiling range of gasoline has a beneficial effect on the octane number of the gasoline.

An object of the invention is preparation of high purity 2-phenylpentane (2-pentylbenzene). A particular object is the conversion of 1,4 bis (3-pentyl-) benzene to a mixture of Z-phenylpentane and l t-phenylpentane, which mixture is predominantly the 2-phenylpentane.

Contacting a feed comprising essentially bis (3-pentyl-) benzene and benzene in a mol ratio of at least about 2 of benzene to di-alkylbenzene, at a temperature between about 0 and +30 C., with liquid HF in an amount at least suflicient to form a distinct acid phase and at least a catalytically effective amount of BF;;, produces a reaction product mixture containing a mixture of phenylpentanes, which mixture is predominantly 2-phenylpentane.

The feed to the process of this invention comprises essentially benzene and the di-alkylbenzene, bis (3- pentyl-) benzene, for example, 1,4 bis (3-pentyl-) benzene. The structural configuration of the 1,4 compound 1s:

The presence of other alkylbenzenes and di-alkylbenzenes, for example, toluene, xylene, isopropylbenzene and ethylbenzene is undesirable as these compounds interfere with the production of a maximum yield of the desired phenylpentane (pentylbenzene). The presence of large amounts of other hydrocarbons which are inert to the action of the HF-BF3 agent adversely affects the yield of the desired phenylpentane. Amounts of these inert hydrocarbons, for example, paraflins in excess of about 3 percent based on his (3-pentyl-) benzene results in the formation of a separate hydrocarbon phase in the reaction zone.

The mol ratio of benzene to bis (3-pentyl-) benzene should be at least 2 in order to maximize the yield of the desired phenylpentane. It is preferred to use more than this amount of benzene. The preferred range of benzene to bis (3-pentyl-) benzene is between about 3 and 6. In other words, at least 1 mol of benzene should be present we I for each mol of pentyl groups present in the feed. And preferably between about 1.5 and 3 mols of benzene per pentyl groups.

The process is carried out under substantially anhydrous conditions. The liquid hydrogen fluoride charged should not contain more than about 2 or 3% of water. Commercial grade anhydrous hydrofluoric acid is suitable for use in the process.

Substantially anhydrous liquid hydrogen fluoride is present in the reaction zone in an amount at least sufficient to form a distinct separate acid phase. More than this amount is desirable. In general between about 3 and 50 mols of liquid HF are used per mol of his (3- pentyl-) benzene charged. The preferred usage of liquid HP is between about 5 and 20 mols.

Boron triiluoride, BFs, must be present in the reaction zone, along with the liquid HP, in at least a catalytic amount. As much as 1 mol of BF3 per mol of his (3- pentyl-) benzene in the feed may be used. More than this amount may be used, but is not necessary. It is preferred to operate with a relatively small amount of BFs, for example, 0.3 mol per mol of bis (3-pentyl-) benzene charged.

The phenylpentanes are readily attacked by the HF BF3 treating agent to form paraffins and condensed ring compounds. In order to minimize these side reactions, the process is carried out at a temperature of not more than about +30 C. The process may be carried out at a temperature of about 0 C. or even slightly lower. It is preferred to operate at a temperature of about +15 C.

The reaction proceeds rapidly at the higher temperatures. For example, a 5 minute contacting time is suflicient at +30 C. Longer times are used as the temperature of contacting is decreased. When operating at about 15 C. it is preferred to use a contacting time of about 15 minutes.

Example The results obtainable by the invention are illustrated by the following example: The run was carried out using a carbon steel reactor provided with a 1725 R. P. M. stirrer. The agent and reactants were added in the following order: (1) 1,4 bis (3-pentyl-) benzene, 0.18 mol (this material had a boiling point of 268 C. and a refractive indexn 1.4857); benzene, 2.25 mols; commercial grade anhydrous HF, 10 mols; and commercial grade BFz, 0.40 mol.

The contents of the reactor were agitated during the addition of the HF and BF3. The contacting was carried out at room temperature, +23 C., for a total time of 15 minutes.

The contents of the reactor were withdrawn into a vessel filled with crushed ice. An upper hydrocarbon layer formed over an aqueous layer. The hydrocarbon layer was decanted and washed with dilute ammonium hydroxide solution to remove HFBF3. The hydrocarbons were then water washed to remove ammonium hy droxide.

The hydrocarbon mixture was fractionated in a distillation column providing about 30 theoretical plates. Each product fraction was analyzed by a combination of boiling point, specific gravity, refractive index, ultraviolet and infrared spectra.

The product distribution in mol percent was as follows:

Pentane The higher boiling fraction had a refractive index n of 1.5200. An analysis showed that appreciable quanto other condensed ring compounds.

tities of indanes and tetralins were present in addition An analysis of the phenylpentane fraction showed it to consist of about 90% Z-phenylpentane and about 10% of 3-phenylpentane.

The water displacement method described in the example for the recovery of the product hydrocarbon mixture is particularly suitable for laboratory operation. In a large scale operation the product hydrocarbons may be recovered by distillatively removing the HF and BFz. The distillative decomposition of the HF-BFs-product mixture should be carried out at a temperature below about +30 0.; preferably the HF and BF3 should be removed at a temperature of about the boiling point of liquid HF. The rate of removal is expedited by the use of a vacuum or an inert stripper agent such as propane.

Thus having described the invention, what is claimed is:

'1. A process which comprises contacting, under substantially anhydrous conditions, a feed comprising essentially (1) benzene and (2) bis (3-pentyl-) benzene in a mol ratio of at least 20, with at least enough liquid HP to form a separate acid phase and at least a catalytically effective amount of El za, at a temperature between about 0 and about +30 C. for a time suflicient for a reaction between benzene and his (3-pentyl-) benzene to take place, and removing HFBF3 to recover a product hydrocarbon mixture which contains appreciable amounts of Z-phenylpentane and 3-phenylpentane.

2. The process of claim 1 wherein the usage of liquid HP is between about 3 and 50 mols per mol of his (3- pentyl-) benzene charged.

3. The process of claim 1 wherein the usage of BFs is between about 0.1 and 1 mol per mol of his (3-pentyl-) benzene charged.

4. The process of claim 1 wherein the mol ratio of benzene to his (3-pentyl-) benzene is between about 5. A process for the production of 2-phenylpentane, which process comprises contacting, under substantially anhydrous conditions, a feed consisting essentially of (1) benzene and (2) 1,4 his (3-pentyl-) benzene in a mol ratio between about 3 and 6 with between about 5 and 20 mols of liquid HF and about 0.3 mol of B53, respectively, per mol of his (3-pentyl-) benzene charged, at a temperature of about +15 C. for a time of about 15 minutes, removing HF and BF3 to recover a product bydrocarbon mixture, and recovering from said product hydrocarbon mixture a fraction consisting of about 90% 2- phenylpentane.

References Cited in the file of this patent UNITED STATES PATENTS 2,385,524 Mattox Sept. 25, 1945 2,396,965 Passino Mar. 19, 1946 2,534,072 Schulze Dec. 12, 1950 

1. A PROCESS WHICH COMPRISES CONTACTING, UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS, A FEED COMPRISING ESSENTIALLY (1) BENZENE AND (2) BIS (3-PENTYL-) BENZENE IN A MOL RATIO OF AT LEAST 20, WITH AT LEAST ENOUGH LIQUID HF TO FORM A SEPARATE ACID PHASE AND AT LEAST A CATALYTICALLY EFFECTIVE AMOUNT OF BF3, AT A TEMPERATURE BETWEEN ABOUT 0* AND ABOUT +30* C. FOR A TIME SUFFICIENT FOR A REACTION BETWEEN BENZENE AND BIS (3-PENTYL-) BENZENE TO TAKE PLACE, AND REMOVING HF-BF3 TO RECOVER A PRODUCT HYDROCARBON MIXTURE WHICH CONTAINS APPRECIABLE AMOUNTS OF 2-PHENYLPENTANE AND 3-PHENYLPENTANE. 